This invention relates to apparatus and methods for noninvasively determining the specific gravity of a fluid, such as urine, through ultrasonic sensing techniques.
It is known to noninvasively sense the characteristics of a biological fluid in a closed collection system through the use of ultrasonic transducers. For instance, in U.S. Pat. No. 4,418,565 of St. John entitled "Ultrasonic Bubble Detector", a pair of ultrasonic transducers are located on opposite sides of a length of flexible tubing to detect air bubbles passing therethrough. Likewise, an automated urinary output monitor is shown in U.S. Pat. No. 4,448,207 of Parrish in which an ultrasonic transducer is used determine fluid level through ultrasonic echo elapsed time measurements.
However, a particular need exists to noninvasively measure the specific gravity of a fluid sample in a fluid collection system which is not achieved by the known ultrasonic sensors since they are not designed to preform this function.